Arrange the following in order of increasing extension.

The order of increasing extension runs Politics of International Relations, Political Science, Social Science, Sciences.

Extension is the range of things a term covers, so the arrangement moves from narrowest to widest.

Politics of International Relations is a specialised branch, so it has the smallest extension.

Political Science contains it, and Social Science is broader still, embracing political science among others.

Sciences is the widest class, taking in the social sciences within it.

So the increasing sequence is 4, 2, 1, 3.